1. Field of the Invention
The present invention relates to a differentially controllable two-way clutch used for a power transmission mechanism and an auxiliary machine driving system in an automobile and configured to transmit and block power in two directions, a forward rotation direction and a backward rotation direction.
2. Description of the Related Art
In general, a two-way clutch is used for a power transmission mechanism and an auxiliary machine driving system in an automobile as means for switching a power transmission path. For example, when a hybrid car with two power sources, an internal combustion engine and an electric motor, travels using the electric motor in addition to the internal combustion engine, power from the electric motor is transmitted to an output shaft through a two-way clutch in both forward and backward rotation directions. Furthermore, as described in Japanese Patent Application Laid-Open Nos. 2002-5200, H6-344796, and H10-53044, the two-way clutch is also used for an auxiliary machine driving system that also uses an electric motor, a center differential in a four-wheel-drive car, and the like.
According to the two-way clutches in Japanese Patent Application Laid-Open Nos. 2002-5200, H6-344796, and H10-53044, a cylindrical surface is formed on one of an inner wheel and an outer wheel, whereas a cam surface is formed on the other of the inner and outer wheels. A torque transmission member such as a roller or a sprag is interposed between the cylindrical surface and the cam surface. The torque transmission member is held in the neutral position of the cam surface or in one of engaged positions of the cam surface. An electromagnetic clutch mechanism or a frictional driving mechanism is used to switch the phase of a cage configured to hold the torque transmission member.
However, in the configuration in which the torque transmission member is held in the neutral position of the cam surface, the torque transmission member is held by bias means provided in the cage. Thus, the torque transmission member cannot disadvantageously be reliably held at the neutral position. On the other hand, in the configuration in which the torque transmission member is held in one of the engaged positions of the cam surface, the cylindrical surface and the torque transmission member are in sliding contact with each other. Thus, while the two-way clutch is inactive (running idly), drag torque is generated, resulting in a disadvantageous increase in fuel consumption or the like.